I think it partially depends on how much you want to do on your own, and how much you want to do with a guide. For example, you could try something like Village Life where you arrive in a village and then someone from that village will take you around, and you can stay with a family there. Its a great way of getting closer to the community as opposed to passing through and snapping a few photos.
However, if you want to hire a guide to take you around more places, to handle transport, etc. then one guy I'd recommend is Daniel at Via Translyvania. He's great and the prices are very reasonable.
-Greg